This is a facinationg subject and I remain somewhat clueless so can some -one explain what Vertical RNP is measuring whenit is utilized during an Integrated Navigation Approach. This is a term coined by Boeing for the IAN capabilty that is available, if not standard in the B737NG and B787 aircraft. Basically there is a 400' wide decent path created that looks like a glideslope and whether it be one mile or twenty-five miles from the MAP, it remains only 400' wide, unlike a ILS glideslope that expands in depth as it moves back from the MAP or runway TDZ. Sort of like a tube that descends to the MAP. This is different than say a VNAV approach and you utilize a glideslope just as you would in an ILS approach. During this approach a visual glidesople along a visual RNP and ANP pointers are presented for both lateral nav and vertical nav.
So the question remains in my mind just what are we looking at when we see vertical RNP values. Might menton that the vertical RNP/ANP scales do not appear until we wre excactly 1,024 feet above the MAP.
